Cosmochemical study on parent body evolution of chondritic meteorites

球粒陨石母体演化的宇宙化学研究

基本信息

批准号：
08454167
负责人：
EBIHARA Mitsuru
金额：
$ 1.15万
依托单位：
TOKYO METROPOLITAN UNVERSTY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

1. Distribution of rare earth elements, thorium and uraniumThese elements are largely distributed in Ca-phosphate minerals in equilibrated ordinary chondrites. Considering that Ca-phosphates are soluble in acid, chondritic meteorites were separated into acid-soluble and acid-residual phases. Then, rare earth elements, thorium and uranium were precisely determined for the acid-residual phases by inductively-coupled plasma mass spectrometry. The acid-residual phases consist of pyroxene, plagioclase and glass; glass is more abundant than plagioclase in unequilibrated ordinary chondrites. Rare earth contents and their abundance pattern normalized to their cosmic abundance for acid residual phases are correlated with the degree of thermal metamorphism chondrites experienced on the parent body. Similar change was observed for thorium and uranium contents. From these results, it was observed that contents of rare earth elements, thorium and uranium are good parameters for describing the thermal activity chondrites suffered on the parent body(ies). Furthermore, these contents are also correlated with contents of noble gases, especially heavy noble gases, suggesting that these noble gases were released from chondrites and were degassed from the parent body(ies) upon heating due to thermal activity.2. Refractory siderophile element abundances in metallic phases of ordinary chondritesOrdinary chondrites mainly consist of silicates, sulfides and Fe-Ni alloy phases. The weight of Fe-Ni phases ranges from several % up to 20% and siderophile elements are quantitatively distributed in metal phases. Precise determination of refractory siderophile elements revealed that their abundances systematically change from group to group of ordinary chondrites. Such a change was suggested to be caused by the difference in accretion temperature of ordinary chondrite parent bodies.

1。稀土元素，thor元素和铀这些元素的分布在很大程度上分布在平衡的普通软骨中的Ca-磷酸盐矿物质中。考虑到碳磷酸盐可溶于酸，将软骨陨石分离为酸溶性和酸性相。然后，通过电感耦合的血浆质谱法精确确定了稀土元素，thor和铀和铀。酸性相位由辉石，斜长石和玻璃组成。玻璃比未平衡的普通软骨中的斜长石比斜长石更丰富。稀土内容及其丰度模式正常于其对酸残留相的宇宙丰度，与母体上经历的热变质软骨的程度相关。观察到类似的变化，thor和铀含量也是如此。从这些结果中可以看出，稀土元素，thor和铀的内容是描述母体上遭受的热活动软骨的良好参数（IES）。此外，这些内容还与贵重气体（尤其是较重的贵重气体）的内容物相关，这表明这些贵重气体是从软骨中释放出来的，并在热活动引起的加热后从母体（IES）脱发。2。普通软骨软骨的金属阶段的难治性铁质元素丰度主要由硅酸盐，硫化物和Fe-Ni合金阶段组成。 Fe-Ni相的重量范围从几％到20％，而铁质元素在金属相中定量分布。对难治性的副元素元件的精确确定表明，它们的丰度从系统中从组中变为普通软骨。提出这种变化是由普通软骨母体的积聚温度差异引起的。